Radiation Sources

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

1

Radiation Sources• Heavy nuclei are unstable against spontaneous emission of particles.• Barrier penetration.• Higher energy ► easier penetration ► short half-life ► less practical.• Lower energy ► less penetrability ► long half-life ► less activity.• Most sources ► 4-6 MeV.• Investigate the famous alpha sources and the corresponding energies and branching ratios.• Most famous is 241Am. Smoke detectors.• Short range ► thin sources.• Q-value.• Recoil.• Kinetic energy of as a function of Q.• Nuclear reactions as sources of ’s.

HW 2HW 2

Density effect & units of thickness.

En

erg

y R

eso

luti

on

Energy loss.Neutron source?

Modes of decay.

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

2

Radiation Sources

HW 3HW 3

Different units used for sample (or target) thickness

Charged particles.

Gamma.

Continuous energy loss.

Catastrophic.

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

3

Radiation Sources

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

4

Radiation Sources• Spontaneous fission.• Transuranic isotopes (example 252Cf).• Also alpha emitters.• Two fragments (and few neutrons) per fission.• Fragments are positive ions (highly charged ~ Z).• Strong energy loss.• Usually thin coating on a flat backing.• Only one fragment per fission escapes the sample.

Heavy

Ligh

t

?

Indu

ced

Source of fragments and

neutrons.

HW 4HW 4

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

5

Radiation Sources• Many laboratory sources are sources.• Needs to be relatively thick source.• Parent half-life and daughter energy!• Catastrophic interaction.• Energy and efficiency calibration.• If for efficiency calibration, source needs to be thin, or correction factors.correction factors.• Small “width” compared to best detector resolution.• Activity and effect on calibration.

Annihi

lation

TOI is TOI is better!better!

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

6

HW 5HW 5

Radiation SourcesRelative intensity I

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

7

Signal Processing - Introduction

PHA

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

8

Radiation Sources

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

9

Radiation Sources• Laboratory sources limited to < 3 MeV.• How can we get the 6.13 MeV transition in 16O?• 27Al(p,) and other charged particle induced reactions (could suffer Doppler effectDoppler effect).• Also neutron induced reactions.

Energy loss.

Stopping power.

HW 6HW 6

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

10

Radiation Sources• Bremsstrahlung from fast electrons.• Continuum.• High energy electrons and high Z material.• Filters.

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

11

Radiation Sources

K

K

• Energy increases with Z.• Fluorescent yield Fluorescent yield (competing Auger).• Self absorption; source thickness.• Different excitation mechanisms:

EC (accompanied by and/or inner bremsstrahlung IB. (511?). IC (accompanied by bremsstrahlung). Incident “beam” on a target, low Z ► soft X-rays; high Z ► hard X-rays.

X-ray“XRF”

Electrons: X-ray exit window at large angles.Lining shield.

• Characteristic X-rays. Elemental analysis.

Project 2Project 2PIXEPIXE

Clean

http://www.kayelaby.npl.co.uk/atomic_and_nuclear_physics/4_2/4_2_1.html

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

12

Radiation SourcesPIXEPIXE

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

13

Radiation Sources

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

14

Radiation Sources

Synchrotron radiation.

Radiation Detection and Measurement, JU, First Semester, 2010-2011 (Saed Dababneh).

15

Radiation Sources

Neutron sources

• We will discuss neutron sources later.• You are asked to prepare your own presentation on this subject.• Don’t limit yourself to Knoll.